1. Field of the Invention
The present invention relates to sequential image display systems and more particularly to an exposure fixture and method for creating mosaic transparencies used for sequentially exhibiting multiple images in an advertising display.
2. Description of the Prior Art
Point of sale advertising is a commonly used tool for product exposure wherein static banners or video displays convey images of a particular product message to the shopping public, usually inside a store where the product is regularly sold. A unique compromise between banners and video marketing in this field involves the use of compact advertising devices which sequentially display several different images. Employing a single transparent mosaic containing multiple images interlaced therein, individual images are viewable for set periods of time from a single back lighted screen. An overlay mask blocks the back lighting from illuminating areas of the transparency sheet associated with images of other subjects during each sequential viewing of a subject selected from the screen. Such devices provide advertisers with a high degree of flexibility for a great variety of exposure of different images within the limitations of a relatively confined space which may be available at such a location typically associated with high concentrations of potential purchasers, such as at a shopping mall or the like.
Transparencies used with sequential image display systems often include a translucent image screen comprising a mosaic of discrete images formed by relatively small interlaced translucent pixels or window segments which are arranged in uniform groups. Pixels corresponding to a discrete image occupy the same relative position in each group and bear corresponding relative magnitudes of translucency. A mosaic of this type is disclosed in U.S. Pat. No. 4,897,802 to Atkinson et al, assigned to the assignee of the rights in the instant application.
A variety of exposure fixtures and methods have been disclosed for making single sheet negative transparencies containing multiple images for subsequent individual display in a selected sequence. Commonly referred to as "step and repeat" registration systems, some of these devices provide a positioning fixture for multiple image exposures onto a single sheet of film. One such device, shown in U.S. Pat. No. 4,142,794 to Trump, discloses a stage upon which photosensitive film is mounted. The stage is moveable along a horizontal plane defined by two perpendicular drives, and enclosed within a glass covered housing. Elevated above the stage are two parallely spaced tape lengths securing an image bearing negative. A light source positioned above the secured negative provides a light beam capable of projecting the image onto a particular section of the film, with the remainder of the film obscured from the light. Incrementally re-positioning the film after each successive exposure is a stepping motor and a control circuit, resulting in an exposed sheet of film containing separated multiple images.
Step and repeat exposure methods associated with the type of fixture described above generally begin by exposing a particular negative onto an unmasked portion of film. Next, the "step and repeat" fixture is utilized in an effort to precisely move either the film or a mask to the corresponding location for the next image to be exposed. The process repeats as desired until the film is completely exposed. Although offering advantages for close tolerance positioning and adequate to expose multiple images onto single sheets of film, the disclosed methods generally do not create images which are interlaced among other images throughout the film surface for efficient display of selected ones of such images for set periods of time. Rather, each print is set onto its own particular section of film, often resulting in only rows and columns of picture segments.
The Atkinson patent overcomes the "interlacing" problem above by providing a specially masked fixture. The fixture is part of an exposure system, comprising a camera and a framework for mounting a projector. A mirrored, folded light path is provided through the framework for columnating the light to obtain full size pixels. This mirrored path is necessary to minimize divergence of the projected light from the light source, often causing shadowing and oversizing of exposed pixels due to the relatively small sizing of the mask apertures through which the projected light passes. The system further includes a mask capable of obscuring and passing preselected segments of light, and a moveable vacuum mount with film mounted thereon. Corresponding to the pixel spacing, the mount is intended to be moveable 0.013 inches right, left, up and down.
The corresponding method of fabrication used with the Atkinson fixture begins by supplying an image bearing negative along with a full size sheet of film. The fixture mask allows "segments" of the overall image to be exposed onto the film, while still preserving the overall image likeness. Projecting the image onto the masked film initiates the exposure process thus exposing a portion of the transparency with the image. Next, a new negative is supplied and the process repeated. After four such exposures, the resulting transparency forms a mosaic having groups of interlaced pixels corresponding to the four discrete images. Although offering some benefits in that the Atkinson fixture and method offers a movable mount and a light obscuring mask to interlace the images, due to the fact that the device is large and relatively complex because of the mirrored path, it has not gained general commercial acceptance.
A further limitation often affecting prior art mosaic fixtures and methods involves a phenomena commonly referred to as "white flash", which often compromises the quality of the finished product. Representing bright border streaks adjacent to opaque pixel boundary lines, "white flash" detracts from the quality of the image presentation during an image transition, causing attention to the bright aberrations momentarily observable on the display viewing surface. Careful exposure techniques using the hereinabove methods may result in a transparency free from "white flash", however, such techniques often require exact alignment between the exposure mask and film to prevent exposure voids between pixels. Such time consuming care creates a more costly finished product and renders the quality of such product highly dependent on the care and skill exercised by the operator.
Thus the need exists for a straightforward and efficient display mosaic fabrication fixture having the capability of controllably and precisely relatively positioning a mask relative to a sheet of film for creating a display mosaic image characterized by individual image pixels interspersed with pixels of other images over the face of the sheet of film for subsequent selected illumination of the selected pixels of the respective images. Additionally, the need exists for a more efficient method for creating mosaic transparencies free from "white flash".